The present invention relates to novel tetrazolylcoumarin derivatives and their salts, and further to a process for the preparation thereof and a pharmaceutical composition containing the tetrazolylcoumarin derivatives or their salts as an active component.
It is known that a certain kind of coumarin derivatives have an antiallergic activity. For instance, Japanese Patent Unexamined Publication No. 64273/1975 discloses that coumarin compounds of the following general formula: ##STR2## wherein X is an alkyl group or an aryl group, X.sup.1, X.sup.2, X.sup.3 and X.sup.4 are the same or different and each is hydrogen, nitro group, an alkyl group, an alkoxyl group, an aryl group, an aralkyl group, a heterocyclic group, a halogen atom, carboxyl group or an acyloxyl group, and any adjacent two groups of X.sup.1, X.sup.2, X.sup.3 and X.sup.4 may form a substituted or unsubstituted condensed carbon or heterocyclic ring with the carbon atoms bonding thereto, show an antiallergic action. However, these coumarin derivatives are not always satisfactory antiallergic agents.
It is an object of the present invention to provide novel tetrazolylcoumarin derivatives.
A further object of the invention is to provide tetrazolylcoumarin derivatives useful as antiallergic agents.
A still further object of the invention is to provide a process for preparing tetrazolylcoumarin derivatives.
Another object of the invention is to provide a pharmaceutical composition containing tetrazolylcoumarin derivatives or their salts as active components, which is useful for preventing and treating allergic diseases.
These and other objects of the invention will become apparent from the description hereinafter.